Control of high frequency generators



Feb. 5, 1935. 5 1,990,216 CONTROL OF HIGH FREQUENCY GENERATORS Filed July 2. 1929 Q. I I Fanalaing o Device I INVENTOR ERICH AscH.

ATTORNEY Patented Feb. 5, 1935 PATENT OFFICE CONTRDL OF HIGH FREQUENCY GENERATORS Erich Asch, Berlin-Sudende, Germany, assignor I to Radio Patents Corporation, New York, N. Y.,

a corporation'of New York Application July 2, 1929, Serial No. 375,459

' In Germany July 5, 1928 9 Claims. (01. 179-111) This invention relates to a modification of the arrangement described in 11.8. Patent No.

A continuous current amplifier accordingto the application above referred to can be adapted in a known manner to operate as a generator of oscillation'sby the current in the output circuit being back-coupled to the grid of a preceding thermionic tube.

One object of the invention is to provide a system for translating capacity variations into electrical variations. Another object of the in- ,vention is to provide a. capacitative control system having increased sensitivity as compared to similar systems known in the prior art. The new features and further objects of the invention will be set forth in more detail in the following description in conjunction with the accompanying drawing illustrating a circuit embodying'the invention. Figure 1 shows one form of a circuit arrangement in accordance with the invention utilizing a direct coupled system as described.

in my above mentioned U. S. patent.

- Figure 2 illustrates another circuit embodying the invention applied to an audio frequency amplifier. I

Figure 1 of the accompanying drawing illustrates this arrangement for such an amplifier having an end tube 2 and a preceding tub 1. The output circuit of the final tube cont a coil 9 which reacts on the coil oint e oscillatory grid circuit of the tube 1 comprised of the inductance '7 and a variable condenser 8. anode circuit of thefinal tube further contains an indicating device or any other suitable translating device 11 which is shunted by a condenser 12, the said indicating device consisting, according to requirements, of a measuring instrument, an ohmic resistance, the primary coil of a'trans- 2 and resistance means 3, 4, 5, and 6 are in-'-- serted in the anode and cathode leads to produce proper. potentials for the ,tube. electrodes. Experiments have shown that the magnitude of the electrical oscillations thus produced, is

dependent upon the size of -a condenser 10 or any other electrostatic control devicewhich is connected in parallel with the anode resistance 3 of the tube 1. The capacity of this condenser need not exceed 10-100 centimeters according to the wave length of the oscillatory circuit 7,8.

the electrostatic device 10 is an electrostatic.

The

Owing to the rectification which is produced in the amplifier, the current in the output circuit varies within wide limits with the size of the condenser 10.. This can be utilized in many ways; thus, for instance, the condenser 10 may 5 consist of. two small parallel plates which are arranged close together and the distance between which can be varied. The current in the output circuit is then an indication of the distance between the said plates. In this way a very sensi- 1 tive me g instrument is obtained for small distances, which may for instance be used for the registration of mechanical oscillations. If the plates of the condenser are fixed, the current in the output circuit measures the di-elec-- tric constant of the medium between the plates. By this .means it is, for instance, possible con-' tinuously t6 check the moisture content of a cur-; rent of steam flowing between the plates,'etc;. If 6 microphone such as of the type shown in Fig. 2 and the translating or indicating instrument 11 a loud speaker, the system becomes an audio am-' plifier which may be 'used for various purposes. such as for modulation of a radio transmitter and the like. In the later case, the translating device is merely replaced by the modulating audio transformer of the transmitter. A great advantage in this case is that, in-contradistinction to other arrangements, the condenser 10 does not appertainto a circuit which oscillates'with resonance frequency or in its proximity.-

In the latter case, the electrostatic telephone must be arranged at a small distance from the amplifier owing to the disturbing capacity of the leads, and therefore also the source of the sound mustv be near the amplifier. It it is desired to avoid this, the source of sound may be. arranged to act first of all on a microphone of any other 0 desired type and the speech currents be transmitted over a distant line and lead-to a telephone, the diaphragm of which belongs to an electrostatic telephone. 1

Figure 2 illustrates an arrangement according 5 to the invention for amplifying audio frequency currents. Similar reference numbers identify similar parts as those in Figure 1. This circuit merely differs from Figure 1 in thata combined electrostatic telephone and microphone .device 0 is provided in place of the condenser 10 consisting of a common diaphragm' 15 and two stationary grid-like electrodes 13 and 14 disposed each opposite one side of the diaphragm 15. The diaphragm 15 in combination with the electrode 13 isarrangedtoactasareceiver andthe combination of diaphragm 15 and the electrode 14 acts as an electrostatic microphone connected in parallel tothe anode resistance 3 in a manner similar to Figure 1. The receiving part of the electrostatic device is shown to be controlled by audiofrequency currents supplied by a microphone system of any type comprising microphone 18, battery 19, and transformer 1'1. It is understood from the'above, that-a single electrostatic microphone may be arranged directly operated by the sound vibrations. In this manner, the oscillations produced by the tube 1 are modulated in accordance with the sound vibrations,

rectified by the tube and applied to the tube 2 by virtue of the direct coupling for further amplifi cation. An audio frequency transformer 16 is shown inserted in 'the anode circuit of the second tube in place of the indicating instrument according to Figure 1 for further utilization of the amplifiedsound currents for any desiredv purpose such as for modulating a radio transmitter. e

In all the arrangements the condenser 10 may be protected against the anode voltage on one or both sides by means of blocking condensers and, if necessary, it may contain a leak resistance, so that it can'ies high frequency currents only.

The arrangement hereinbefore described may otherwise be modified without in any way departing from the spirit of the invention.

What I claim is:

1. A system for controlling electric currents, an amplifier comprised of at least two thermionic tubes having cathode, anode, and control electrodes, the anode of the first tubebeing directly connected tothe grid of the second tube, a coil inserted in the anode circuit of the second tube and arranged to react on the control circuit of the first tube, whereby the amplifier is caused to oscillate as a generator, a high resistance in the anode circuit of the first tube, a variable electrostatic control device in shunt with said high resistance to modulate the oscillations of said oscillator, and a direct current responsive translating device in the anode circuit of the second tube.

2. An electrical system comprising a plurality of discharge tubes, said tubes being arranged in cascade with direct coupling connections from one tube to a succeeding tube; a resonant circuit connected to one of said .tubes; means whereby the first tube operates as an oscillator by regenerative feed back from the output of a succeeding' tubeyan electrostatic control device in the output circuit of said oscillator to modulate the oscillations produced by said oscillator; and a translating device in the anode circuit of a succeeding tube to said oscillator.

3. An electrical system comprising a plurality of electron discharge tubes having cathode, anode and grid electrodes, said tubes being arranged in cascade with direct conductive cou-' pling connections from one tube to a succeeding tube; means including a resonant grid circuit'for the first tube for producing electrical oscillations by a regenerative feed back from the anode cir- 3 in which said electrical device is comprised of an electrostatic microphone; and an audio frequency translating device inserted in the anode circuit of the last tube.

5. In an electrical system comprising a first thermionic tube; a second thermionictube, said tubes havinganode, cathode and control electrodes; a source of anode voltage supply; means for directly and conductively connecting the anode electrode of said first tube to the control electrode of said second tube; connections from the anode of each of said tubes to the positive terminal of said source; further connections from the cathode of'each of said tubes to the other terminal of said source; resistance means in said anode and cathode connections to produce proper mutual operating potentials for said tubes; a resonant grid circuit for said first tube for producing electrical oscillations through energy feed back from the anode circuit of said second tube; an electrostatic control device connected. in parallel to said resistance means in the anode lead of said first tube to modulate the oscillations produced by said oscillator; and a translating device in the anode circuit of said second tube.

6. An electrical system as described in claim 5 in which'said electrostatic device is comprised of'an electrostatic microphone and an audio frequency translating device inserted in the anode circuit of said second tube.

'7. In an electrical system comprising a pair of discharge devices connected in cascade; means including a feed back connection from said second device to said first devicewhereby the first device operates as a detector-oscillator; further means for modulating the oscillations generated by said oscillator, said last means being connected in the anode circuit of said first device; and a translating device in the output of thelast device. 7

8. In an electrical system; a plurality of discharge devices-each comprising a cathode, anode and control electrode, the output electrode of one device being directly coupled to the succeeding device; means including a resonant circuit connected in feed back with said first device for Y modulating said oscillations; and a. translating device. 7

9. In an electrical system; a plurality of discharge devices each comprising a cathode, anode and control electrode, one device being directly and conductively coupled to the succeeding device; means including a resonant circuit connected to the control electrode of the first dis-, charge device and a feed back connection thereto from a succeeding device whereby said first device operates as a detector-oscillator; an electrostatic control device connected to a further of said discharge devices other than said mentioned discharge device connected in feed back for said that device; and a common operating source supplying anode current for said devices, the cathodes of said tubes being connected in series across said source together with a resistance means to secure proper cathode heating current.

- ERICI-I- ASCH. 

